The aim of this study is to minimize the thickness (or weight) of laminated composite plates subject to both in-plane and out-of-plane loading. A new variant of the simulated annealing algorithm is proposed to optimize the lay-up design. Fiber orientation angle and number of plies in each lamina are used as design variables. Considering static failure as the critical failure mode, the maximum stress and Tsai-Wu criteria are used together to predict failure. Numerical results show that the optimization methodology proposed in this study can find the globally optimum laminate designs even with a high number of design variables. (C) 2011 Elsevier Ltd. All rights reserved.